PFAS testing is particularly sensitive to sample handling protocol given the contaminant’s presence in many common consumer plastics.
- Use only the specific PFAS-appropriate sample container your lab provides to avoid contamination.
- Avoid certain personal care products immediately before sample collection per your lab’s guidance.
- Use consistent lab and methodology across retests for meaningful trend comparison.
- PFAS testing is particularly sensitive to these protocol details given the contaminant’s presence in many common products.
Sample Container Contamination
Using the wrong type of sample container (rather than the specific PFAS-appropriate container your lab provides) can introduce contamination given PFAS’s presence in many common plastics and treated fabrics.
The reason PFAS sampling is fussier than other water tests is that the compounds are in the sampling equipment itself unless the equipment was chosen specifically to exclude them. PFAS chemistry is used for non-stick and stain-resistant properties across an enormous range of manufactured goods, which means ordinary laboratory and household plastics can contribute contamination at exactly the trace concentrations the test is trying to measure.
This is why the kit ships with its own containers and why substituting is not a minor deviation. Reusing a bottle from a previous test, rinsing the provided container before use, or decanting the sample into something else can each introduce or remove analyte in ways that make the number meaningless. Some kits also include a preservative in the bottle, so rinsing removes something the method depends on.
Follow the flush instructions exactly as written rather than by analogy to other water tests. Some protocols call for a specified flush before collection and others explicitly want first-draw water, and those two instructions answer different questions. Guessing between them produces a result that does not correspond to what you thought you were measuring.
Personal Care Product Cross-Contamination
Some personal care products contain PFAS — avoid wearing certain cosmetics, sunscreens, or using certain products immediately before sample collection per your lab’s specific guidance.
The guidance about cosmetics and clothing reads like superstition until you know that PFAS is used in water-resistant and stain-resistant treatments, which puts it in some cosmetics, some sunscreens, waterproof outerwear and treated upholstery fabrics. The concern is transfer from your hands or sleeves to the sample at trace levels.
The practical version is short. Wash hands with plain soap and water rather than anything labelled water-resistant or long-wearing, skip lotions and cosmetics on the morning of collection, avoid handling the inside of the cap or the bottle rim, and do not collect while wearing waterproof or stain-treated clothing that could brush the sample.
Avoid the surrounding environment as a contamination source too. Do not set the open container down on a treated fabric surface, do not collect near food packaging with grease-resistant coatings, and do not use a plumber’s tape or fixture attachment that was not part of the kit.
Inconsistent Methodology Across Retests
Using different labs or analytical methods across retests can make trend comparison unreliable — use a consistent lab and EPA-approved method where possible.
Comparability is the point of a retest, and it is easy to lose without noticing. Different laboratories may run different analytical methods with different target compound lists and different reporting limits, so two results that look directly comparable can be measuring meaningfully different things.
Reporting limits deserve particular attention, because a non-detect result only means the compound was below the laboratory’s limit of detection rather than absent. A laboratory reporting down to 2 ppt and one reporting down to 10 ppt can both truthfully return non-detect on the same water, and the second result carries far less information given that the EPA’s enforceable limit is 4.0 ppt for PFOA and for PFOS [1]. Read the reporting limit on the report before you read the result.
The fix is procedural rather than technical. Keep every report, note the laboratory, the method and the reporting limit alongside each result, and return to the same laboratory for retests where you reasonably can. If you do change laboratories, expect to compare the two reports as separate baselines rather than as points on one trend line.
Sample timing carries the same comparability problem. Collecting from a different tap, at a different time of day, or after a different flush duration than last time introduces variation that has nothing to do with a change in your water.
FAQ
Why does my PFAS test kit come with special instructions about clothing and cosmetics?
PFAS is present in many treated fabrics and some personal care products — following your lab’s specific collection protocol avoids introducing contamination that could skew your results.
Can I use my own bottle if I sterilise it thoroughly?
No, and sterilising does not address the issue. The concern is PFAS present in the container material itself rather than microbial contamination, so a scrupulously clean ordinary bottle can still contribute the exact compounds being measured. Use the container the laboratory supplied.
Should I rinse the sample bottle before collecting?
Not unless the instructions specifically tell you to. Many PFAS kits ship containers that are prepared for the method and some contain a preservative, so rinsing can remove something the analysis depends on.
What does a non-detect result actually mean?
That the compound was below the laboratory’s reporting limit, not that it was absent. Check what that limit was, since a laboratory reporting down to 10 ppt tells you much less than one reporting down to 2 ppt when the enforceable limit is 4.0 ppt.
Does it matter if I use a different lab for my retest?
It can matter a great deal. Different laboratories may use different methods, cover different compound lists and report to different limits, which makes results harder to compare over time. Where you can, retest with the same laboratory and the same method.
Follow your specific lab’s PFAS sample collection protocol exactly, including any clothing/cosmetics guidance, to avoid contamination.
References
- Per- and Polyfluoroalkyl Substances (PFAS). U.S. Environmental Protection Agency
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
